Through the years flexible bags have been used as containers for various products, and in this regard, a variety of structures has been employed to serve as closures for such containers. U.S. Pat. No. 1,798,945, which issued to Alfred Lamarthe on Mar. 31, 1931, for example, discloses a self-closing device for flexible openings in articles such as bags, purses, or tobacco pouches. The Lamarthe patent contemplates a pouch having an open upper portion, with such open portion being provided with a pair of cooperating steel springs for closure thereof. The springs are to be formed of steel bands having a convex side and a concave side, and are arranged on opposite sides of the open upper portion of the pouch such that their concave portions face one another and the interior of the pouch. The pouch is opened by exerting pressure sufficient to move the springs apart from one another in their middle portion, and the springs automatically snap the pouch closed upon release of such pressure.
Another closure for flexible receptacles is described in U.S. Pat. No. 3,272,248, which issued to F. J. O'Farrell on Sept. 13, 1966. The O'Farrell patent shows flexible bags formed from two sheets of superimposed flexible material attached along three of their adjoining edges. A pair of resilient stays are attached or embedded in the opposed sheets of flexible material along their unattached edge such that the stays hold the two sides of the bag closely together in a substantially flat, closed condition. The stays may be fabricated to flex more readily in one direction by scoring or slightly deforming one surface of the individual stays. The O'Farrell patent discloses that stays which have been conditioned for preferred flexing in one direction tend to bend in the direction of the surface having the interruptions or score lines therein. O'Farrell teaches that the surfaces of the stays having the interruptions should be placed in face to face relationship so that such tendency to bend will tightly maintain the bag normally closed. The closure may be opened by squeezing opposite sides or edges of the container together, whereupon release of such squeezing force allows the container to automatically close.
A closure that is allegedly stable both in its closed and open conditions is described in U.S. Pat. No. 3,782,601, which issued to A. Krawagna on Jan. 1, 1974. The Krawagna snap-closure is to be mounted on an open corner of a flexible bag and comprises a relatively ridged curved collar portion, a similarly curved but more resilient plate portion, and a flexible web joining the plate and collar portions. Krawagna states that pressure applied to the plate portion deforms such plate portion from a first position through an intermediate dead-center position to a second inverted position. The plate portion is constructed of a thinner and more resilient material vis-a-vis the more rigid collar portion whose stiff trapezoidal cross-section tends to seek its original curvature and thereby hold the thinner plate portion in one of its two positions. In its closed condition, the snap closure tightly pulls the opposite walls of the flexible bag against the curved plate portion thereby sealing the bag. In its open position, the plate portion no longer seals the walls of the flexible bag and the contents of the flexible container can be dispensed through the resulting opening. Another flexible package which allegedly exhibits both a stable closed position and a stable open position is described in U.S. Pat. No. 3,635,376, which issued to H. Hellstrom on Jan. 18, 1972. The Hellstrom package includes a pair of flexible sheet members, specifically an upper membrane sealed to a lower layer, thereby enclosing a containment space therebetween, and forming a dispensing channel along one edge thereof. A ribbed structure is to be formed within the lower layer and acts to block the dispensing channel when the package is in a closed condition. In such closed condition, the upper membrane is stretched over the rib to form a seal across the dispensing channel. To open the package, bending forces are exerted on the rib causing buckling in one or more places along its length. When such buckling occurs along the rib, the upper membrane is no longer tightly stretched thereover and the dispensing channel is no longer sealed. The Hellstrom patent states that the material of the ribbed structure can be selected so that the buckling becomes more or less permanent, or so that the package will spring back into its original closed position upon release of the bending forces in order to reseal the package.
Despite all of the prior work done in this area, there remain problems in effectively providing an easy open/reclose structure for flexible bags which can provide a stable and effective seal for the bag and which can be easily opened to form a stable open condition in such bag. These problems are especially emphasized when larger container openings are desired. With prior art closure devices, stable large openings in flexible containers could not easily be obtained economically. Closure devices which provided good sealing qualities did not offer sufficient access to the interior of the container, while devices which provided substantial access were inconvenient and/or did not offer good sealing characteristics.